Background There are many comorbidities associated with Down syndrome (DS), including obstructive sleep apnea (OSA) and masticatory muscle alteration. Muscular hypotonia, in particular, of the masticatory and oropharyngeal muscles is one of the main characteristics of individuals with DS, resulting in impairments of speech, swallowing, and mastication in these individuals. In addition, total or partial obstruction of the airways during sleep can occur due to pharyngeal hypotonia, leading to snoring and to OSA. This progressive respiratory disorder is associated with a high risk of morbidity and mortality in individuals with DS. The aim of this research is to assess the therapeutic effects of surface neuromuscular electrical stimulation (NMES), the mastication apparatus (MA), and a mandibular advancement oral appliance (OA m ) with an embedded thermosensitive microchip on the functions of masticatory muscles (bilateral masseter and temporal muscles), physiological sleep variables, and salivary parameters in adult patients with DS. Methods The patients with DS will be randomly selected and divided into three groups (DS-NMES, DS-MA, and DS-OA m ) with a minimum of 10 patients in each group. A thermosensitive microchip will be embedded in the OA m to record its compliance. The therapeutic effects on masticatory muscle function will be investigated through electromyography, a caliper, and a force-transducer device; the sleep variables, in turn, will be evaluated by means of polysomnography. The physicochemical and microbiological properties of the saliva will also be analyzed, including the salivary flow, viscosity, buffer capacity, cortisol levels (susceptibility to psychological and/or physical stress), and Pseudomonas aeruginosa levels (risk of aspiration pneumonia) in these patients. The methods determined for this study will be carried out prior to and after 2 months of the recommended therapies. Discussion The primary outcomes would be the improvement and/or reestablishment of the function of masticatory muscles and the physiological sleep variables in this target public since individuals with DS commonly present generalized muscular hypotonia and dysfunction of the oropharyngeal musculature. As a secondary outcome indicator, the impact of the applied therapies (NMES, MA, and OA m ) on the salivary microbiological and physicochemical properties in DS individuals will also be assessed. Furthermore, the compliance of OA m usage will be measured through a thermosensitive microchip. Trial registration Registro Brasileiro de Ensaios Clínicos, RBR-3qp5np . Registered on 20 February 2018. Electronic supplementary material The online version of this article (10.1186/s13063-019-3300-0) cont...

Objective To evaluate the phenotypic features of the masticatory biomechanics in atypical subjects with Down syndrome (DS). Its influence was analysed on sleep disorders, body adiposity and its risks, and some physicochemical properties of saliva. Methods Seventy subjects were enrolled to assess masticatory biomechanical function and divided into two groups: DS and control groups. Electrical activities of the masseter and temporal muscles (at rest and in maximum voluntary clench‐MVC), maximum bite force‐MBF and maximum mouth opening‐MMO were investigated. Among the atypical subjects, just 24 participants underwent the anthropometry, the polysomnography II and the saliva testing (salivary flow rate‐SFR, buffer capacity‐BC and salivary cortisol levels, morning/SC‐AM and night/SC‐PM). Results MVC and MBF values showed high statistical significance in the control group (P < .001) than in the DS group of 35. MMO values were slightly increased in the DS group in relation to the control group. Overweight and obesity were found in both genders. Atypical women showed higher risk to develop cardiovascular‐metabolic diseases than in atypical men. OSA severe was 20% for atypical women and 42.8% for atypical men, whereas snoring index was present in all genders. SFR was reduced in 100% of atypical subjects (hyposalivation in 10% women and 28.5% men). Furthermore, 100% BC, 66.6% SC‐AM and 91.6% SC‐PM showed normal patterns. Conclusion Masseter and temporal muscle hypotonia was found in all atypical subjects with DS. This muscle dysfunction strongly was related to overweight/obesity, risks for development of cardiovascular/metabolic diseases, OSA severity, successive snoring episodes and salivary flow reduction in DS.

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